1. Field of the Invention
This invention relates to substrates, such as game cards and lottery tickets, with hidden images that are made to appear. There are many circumstances wherein it is desirable to print invisible indicia or areas on a paper substrate, and then make those areas visible in a simple and easy manner. Such a need exists in the production of educational forms, security documents, and game cards such as lottery tickets and promotional game cards.
2. Prior Art
Typically hidden images and the technology relating thereto are found in game cards that contain hidden play indicia such as numbers, symbols or messages that indicate whether or not the card is a winner or has a certain value to the player. The play indicia is normally covered by an opaque coating material, for example a latex compound which can be scratched off by the player to reveal the play indicia after the ticket has been purchased or otherwise obtained by the player.
Of importance to the game card industry and in particular the instant lottery industry is security. One method of breaching the security of game tickets is by candling, i.e., a bright light is applied to the game card in an effort to read the play indicia either through the latex covering or the back of the ticket. A number of techniques have been developed to counter candling including the use of a foil layer such as aluminum foil as part of the game ticket. This foil layer blocks visible light and therefore makes it virtually impossible to read the play indicia through the opaque coating. However the use of a foil layer has a number of significant disadvantages including higher costs and recycling problems.
Another approach to prevent candling is to imprint confusion patterns on the ticket. A confusion pattern obscures or otherwise confuses the image of the play indicia when visible light is shined through the game card thus making it difficult or impossible to read the indicia before the latex covering is removed. Confusion patterns may be printed on the back of a lottery ticket. Although confusion patterns printed on the back of the ticket help to prevent candling, other methods exist for compromising the security of the ticket. For example, delamination can be used to overcome the security provided by confusion patterns printed on the back of the ticket. The back ticket layer containing the confusion layer is separated or delaminated from the ticket. Once delaminated, the indicia can be read by candling.
Confusion patterns consisting of irregular opaque areas have also been printed on the top surface of the card stock below the opaque mask. In another technique, to prevent photocopying through the opaque mask, a confusion pattern is printed over the play indicia using a transparent media or a media having a color differing from the color of the play indicia so that the confusion pattern will not obscure the play indicia when the opaque mask is removed by a player. Another confusion pattern is then printed below the play indicia on the card material immediately below the play indicia. One disadvantage of this approach is that unless the upper confusion pattern is completely transparent its existence will be apparent to those individuals who may be considering methods for breaching game card security. In addition the upper confusion pattern as described makes very little contribution to the prevention of candling.
Wicking is another technique that has been used to read the play indicia without having to remove the opaque mask. In wicking a solvent containing alcohols, ketones, acetate, esters, aliphatic or amine solutions is applied to either the back or the front of the game card resulting in the bleed through of an image of the play indicia. This makes it possible to determine if a game card is a winner before the opaque coating is removed. One approach to prevent wicking to place solvent responsive dyes in the opaque coating.
Other more exotic techniques may be used for improperly reading hidden images. For example, microscopic spectrophotometry with a computer controlled stepping stage can be used to map out differences in optical properties between the inks. Filtered light either reflected (including white and dark field) and transmitted light may also be used. Polarized light might also reveal differences between the inks. Other types of microscopic techniques might reveal differences, e.g. Tunneling Electron Microscope (TEM), Scanning Electron Microscope, (SEM) and Atomic Force Microscope (ATM) are some examples.
Additionally, by looking at the material absorption with x-rays, the composition of the different inks might be determined. By detecting which ink dots are of one composition and a second type of ink dots are of a second composition. It doesn't matter what the actual composition is, as long as they are different. By using various analytical techniques such as Neutron Activation Analysis, x-ray fluorescence, electron beam fluorescence, and various other two-dimensional techniques, one could plot the responses as to each ink dot composition and hence, map out the hidden image within the printing.
Still further, by placing a material such as plasticized vinyl, oilpaper, and polyester under heat in direct contact with the back part ink, one may be able to absorb out of the ink enough dye to make the image legible.
Any substrate bearing a hidden image, particularly a game card or lottery ticket, must be able to withstand most if not all of these methods of improperly viewing the hidden image.
The aforedescribed techniques and other techniques for hiding images on printed documents are particularly useful for the production of printed materials for promotion, advertising, game, and novelty devices. One common feature of all of these techniques for hiding images, be it hiding a printed message under a paper cover, label, removable opaque coating or layer, e.g., "Scratch-Off" coating, is that once the opaque layer is removed, the information appears instantly.
Known U.S. Patents relevant to these techniques are: U.S. Pat. No. 5,012,318 to Mayo et al; U.S. Pat. No. 5,213,648 to Vermeulan et al; U.S. Pat. No. 5,213,664 to Hansell; U.S. Pat. No. 5,215,576 to Carrick; U.S. Pat. No. 5,286,061 to Behm; U.S. Pat. No. 5,346,258 to Behm et al; U.S. Pat. No. 5,358,281 to Greig ; U.S. Pat. No. 5,368,334 to Christy et al; U.S. Pat. No. 5,532,046 to Rich et al; U.S. Pat. No. 5,542,710 to Silverschotz et al; U.S. Pat. No. 5,562,284 to Stevens; and U.S. Pat. No. 5,569,512 to Brawner et al. Additionally, European No. 0 608 065 to Behm is also relevant to these known techniques. See also, for example various game card and instant lottery ticket constructions disclosed in U.S. Pat. Nos. 4,174,857, 4,273,362, 4,299,637, 4,725,079 and 4,726,608.
With respect to the more relevant references:
U.S. Pat. No. 5,286,061 to Behm describes validation data that is printed with a developable invisible ink capable of being rendered visible to determine if it is valid by application of a developing agent.
U.S. Pat. No. 5,346,258 to Behm et al describes a game card substrate wherein to enhance the security of the card a confusion pattern is printed with an ink that bleeds in the presence of a solvent that also causes the bleeding of the hidden play indicia.
U.S. Pat. No. 5,368,334 to Christy et al describes a security document having an invisible indicia of hydrophobic toner blended into the paper. The indicia is made visible by passing a conventional marker over it.
Time dependant security products, e.g., badges, are well known in the art. For example, see the following U.S. Patents and applications: U.S. Pat. No. 4,903,254 to Haas; U.S. Pat. No. 5,364,132 Haas et al.; U.S. Pat. No. 4,212,153 to Kydonieus et al.; U.S. Pat. No. 5,107,470 to Pedicano; U.S. Pat. No. 5,364,132 to Haas et al.; U.S. Pat. No. 5,446,705 to Haas et al; U.S. Pat. No. 5,058,088 to Haas; U.S. Pat. No. 4,432,630 to Haas; U.S. Pat. No. 4,542,982 to Haas; U.S. Pat. No. 4,779,120 to Haas; U.S. Pat. No. 5,719,828, to Haas (3.0-011/cip); U.S. Pat. No. 5,699,326, to Haas (3.0-013); U.S. Pat. No. 5,715,215, to Haas (3.0-015); U.S. Pat. No. 5,633,835, to Haas (3.0-017); U.S. Pat. No. 5,602,804, to Haas (3.0-019); U.S. Ser. No. 08/642,914 filed on May 6, 1996, now U.S. Pat. No. 5,822,280, to Haas (3.0-022); U.S. Ser. No. 08/718,268 to Frommer, et al filed Sep. 20, 1996 (3.0-024); and U.S. Ser. No. 08/613,316 filed on Mar. 11, 1996, now U.S. Pat. No. 5,785,354, to Haas (3.0-025).
None of these references teach or suggest the invention described herein.